1. Field of the Invention
The invention relates to a data processing apparatus for data processing an audio signal, to a data processing method, a transmitter comprising the data processing apparatus, a transmitter in the form of a recording apparatus, a record carrier, to second data processing apparatus for reconverting an input signal into a replica of the audio signal, to a receiver comprising the second data processing apparatus, to a receiver in the form of a reproducing apparatus and to a transmission signal comprising a data compressed residual bitstream signal.
2. Description of the Related Art
Data processing an audio signal is well-known in the art. Reference is made in this respect to European Patent Application No. EP-A 402,973, document D1 in the List of Related Documents. The document describes a sub-band coder, in which an audio signal is A/D converted with a specific sampling frequency, such as, 44.1 kHz, and the resulting samples in the form of, e.g., 24-bit words of the audio signal, are supplied to a sub-band splitter filter. The sub-band splitter filter splits the wideband digital audio signal into a plurality of relatively narrow band sub-band signals. Using a psycho-acoustic model, a masked threshold is derived and blocks of samples of the sub-band signals are subsequently quantized with a specific number of bits per sample for each block of the sub-band signals, in response to said masked threshold, resulting in a significant data compression of the audio signal to be transmitted. The data compression carried out is based on ‘throwing away’ those components in the audio signal that are inaudible, and is, thus, a lossy compression method. The data compression described in document D1 is a rather intelligent data compression method and requires a substantial number of gates or instructions, when realized in hardware or software, respectively, so that it is expensive. Moreover, the subsequent expansion apparatus also requires a substantial number of gates or instructions, when realized in hardware or software, respectively.